1. Field of the Invention
The present invention relates to an illuminating device and, in particular, to an illuminating device included in a microscope to illuminate a specimen.
This application is based on Japanese Patent Application No. 2006-136573, the content of which is incorporated herein by reference.
2. Description of Related Art
Examples of illuminating devices used in microscopes include the following.
For example, Japanese Unexamined Patent Application Publication No. 2002-250867 describes an illuminating device that changes the magnification ratio of a light source image projected onto the pupil of an objective lens in order to adjust the size of an illumination area to the size of a charge-coupled device (CCD) imager or the observation field of view of an eyepiece lens.
Japanese Unexamined Patent Application Publication No. 2003-185928 describes an illuminating device that switches between spot illumination and plane illumination. In spot illumination, a collimated light beam is irradiated incident on an objective lens. In plane illumination, a large area of a specimen is illuminated by collecting light on a pupil plane of an objective lens.
Japanese Unexamined Patent Application Publication No. 2004-295122 describes an illuminating device that changes the illumination area by opening and closing a field stop in a total internal reflection microscope.
However, although the illuminating devices described in Japanese Unexamined Patent Application Publication Nos. 2002-250867 and 2003-185928 can change the illumination area in accordance with an area corresponding to the size of an imager or the observable area, the illuminating devices cannot change the illumination area in accordance with the size of an object to be observed, such as a specific portion of a specimen cell or an entire area of a specimen cell.
The illuminating device described in Japanese Unexamined Patent Application Publication No. 2004-295122 changes the illumination area by changing the numerical aperture of light made incident on an objective lens through control of a field stop. Accordingly, part of a light beam is blocked by the field stop, and therefore, the amount of light is disadvantageously decreased.
In fluorescence excitation and light stimulation, it is desirable that illumination is efficiently performed in accordance with the size of an object to be observed or an object to be stimulated, such as a specific portion of an observed cell (e.g., a cell nucleus), one entire cell, or a plurality of cells. In particular, since light stimulation requires strong illumination light, an efficient illumination method is required when an LED (light-emitting diode) light source or an LD (laser diode) light source that tends to emit a small amount of light is used.